Tuesday, November 01, 2011

A little more science

This is a classic:

The Astronomy Picture of the Day has this explanation:

If you drop a hammer and a feather together, which reaches the ground first? On the Earth, it's the hammer, but is the reason only because of air resistance? Scientists even before Galileo have pondered and tested this simple experiment and felt that without air resistance, all objects would fall the same way. Galileo tested this principle himself and noted that two heavy balls of different masses reached the ground simultaneously, although many historians are skeptical that he did this experiment from Italy's Leaning Tower of Pisa as folklore suggests. A good place free of air resistance to test this equivalence principle is Earth's Moon, and so in 1971, Apollo 15 astronaut David Scott dropped both a hammer and a feather together toward the surface of the Moon. Sure enough, just as scientists including Galileo and Einstein would have predicted, they reached the lunar surface at the same time. The demonstrated equivalence principle states that the acceleration an object feels due to gravity does not depend on its mass, density, composition, color, shape, or anything else. The equivalence principle is so important to modern physics that its depth and reach are still being debated and tested even today.


Jean said...

Ha, we were just discussing this video the other day on the way home from our favorite Halloween event, the annual pumpkin drop at Chico State. 4 great scientists get together and discuss their theories of gravity, demonstrating with pumpkins. Newton claimed that the pumpkin and the feather would fall at the same rate in a vacuum. (You can see a video of part of the event on my blog post here.

So this is very timely for me :)

Henry Cate said...

I'm glad you enjoyed the video.

The pumpkin drop looks like a lot of fun.